请注意:本版本的所有临时修订版将包含在您购买时。《通信设备用断路器》UL 489A1范围1.1本标准的要求包括用于通信设备中的分支电路过电流和短路保护的单极或多极直流额定断路器。1.2多极的所有极本标准涵盖的断路器在相同的电势下运行。1.3本标准的要求涵盖额定电压为600伏或以下的设备。1.4本标准旨在与UL 489《塑壳断路器、塑壳开关和断路器外壳标准》一起使用，1.5除非另有规定，否则当本标准中使用“断路器”一词时，指的是用于通信设备的断路器。

Please note: All interim revisions for this edition available at time of your purchase will be included.Circuit Breakers for Use in Communications EquipmentUL 489A1 Scope1.1 The requirements of this standard cover single pole or multi-pole DC rated circuit breakers intended for use as branch circuit overcurrent and short-circuit protection in communications equipment.1.2 All poles of multi-pole circuit breakers covered by this standard operate at the same potential.1.3 The requirements of this standard cover devices rated 600 volts DC or less.1.4 This standard is intended to be used with the Standard for Molded-Case Circuit Breakers, Molded-Case Switches and Circuit-Breaker Enclosures, UL 489, as the requirements of this standard modify tests described in that standard.1.5 Unless otherwise specified, when the term "circuit breaker" is used in this standard, it refers to a circuit breaker intended for use with communications equipment.